The mammoth scale of two Toronto-area marijuana grow-operations busted on the weekend shows that "commercial marijuana factories have reached epidemic proportions in Ontario," police said Monday.

A joint operation by officers of the Ontario Provincial Police and the Barrie Police Service at a former Molson brewery, a stone's-throw from a busy highway, turned up thousands of plants. A raid on another building nearby netted thousands more plants. The total street value of the drugs is estimated at $30-million.

Nine people were arrested at former brewery during the raid early Saturday morning.

Deputy Commissioner Vaughn Collins, of the OPP Investigation and Organized Crime Command, said that the grow-op in the former brewery was the "largest and most sophisticated" in Canada. He said that marijuana grown in Canada is routinely shipped to the U.S. and traded for cocaine that it then smuggled back into Canada.

Police said that the operation covered more than 60,000 square feet of space and had been set up to operated 24 hours a day. There were dormitory-type living quarters for up to 50 workers, outfitted with beds, televisions, fridges and stoves. The site was outfitted with over 1,000 high-powered lights and was capable of producing as many as three or four crops annually.

"You had to see it to believe it," OPP Superintendent Bill Crate said after touring the operation. Another officer said that the marijuana plants "went on and on" and compared the site to "a little Saskatchewan."

Barrie police Chief Wayne Frechette told a news conference Monday morning that this was more of a "big-box" enterprise than a "mom-and-pop" operation. "The fact that it resided in our community demonstrates the need for the public to be vigilant for suspicious activities which may be evidence of illegal drug production," he said.

Molson closed the brewery in 2000 and sold it to a company that leases spaces to about half a dozen businesses. The other companies included trucking companies and a bottling company, police said.